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Measuring small current, complicated
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exe:
Diodes are temperature-sensitive and self-heating.

So far I like idea with two independent opamps, but it can be time-consuming to tune the transition region.

Or one can infer active power consumption from measuring average consumption and idle consumption.

But I still don't get what the original problem is.
GeorgeOfTheJungle:
Yes, it's an interesting problem.
tggzzz:

--- Quote from: exe on November 08, 2018, 01:11:51 pm ---Diodes are temperature-sensitive and self-heating.

So far I like idea with two independent opamps, but it can be time-consuming to tune the transition region.

Or one can infer active power consumption from measuring average consumption and idle consumption.

But I still don't get what the original problem is.

--- End quote ---

If operated as I suggest, who cares if the diodes are temperature sensitive and self-heating?

I should have been more specific. I would have thought that my description, especially the first paragraph and "<~0.6V", would have indicated the technique is for measuring the inactive low current, not the active high current. The latter is easy.

Apart from that, if you don't get the original problem, then it is difficult to generate suitable solutions!
exe:
Ah, right, sorry, I thought measurements were to be done across the diode, so would be used as an "exponential resistor". Got it, it the way to switch shunts.


--- Quote from: tggzzz on November 08, 2018, 02:31:22 pm ---Apart from that, if you don't get the original problem, then it is difficult to generate suitable solutions!

--- End quote ---

Exactly, but what meant is: "Gavin Melville, please clarify why you need what you are asking".
t1d:
@ Gavin:
I built out Joshua's circuit. Think I have an extra. If you think it would be helpful, you would like one, gratis, and you are in the USA/48, send me a pm, with your address.







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